let _Vue = null
export default class VueRouter {
    static install(Vue){
        console.log(Vue)
        // 判断当前插件是否已安装
        if(VueRouter.install.installes){
            return
        }
        VueRouter.install.installes = true
        // 把vue构造函数记录到全局变量
        _Vue = Vue
        // 把创建的vue实力时传入的router对象注入到vue实例上
        // 混入
        _Vue.mixin({
            beforeCreate(){
                console.log(this.$options.router)
                if(this.$options.router){
                    _Vue.prototype.$router = this.$options.router
                    this.$options.router.init()
                }
            }
        })
    }
    constructor (options){
        
        this.options = options
        this.routeMap = {}
        this.data = _Vue.observable({
            current:'/'
        })
    }

    init(){
        this.createRouteMap()
        this.initComponents(_Vue)
        this.initEvent()
    }

    createRouteMap(){
        // 遍历所有路由规则把路由规则解析成键值对的形式 存储到routeMap中
        this.options.routes.forEach(route => {
            this.routeMap[route.path] = route.component
        })
    }

    initComponents(Vue){
        Vue.component('router-link',{
            props:{
                to: String
            },
            // template: '<a :href="to"><slot></slot></a>'
            render(h){
                return h('a',{
                    attrs:{
                        href:this.to
                    },
                    on:{
                        click:this.clickHandler
                    }
                },[this.$slots.default])
            },
            methods:{
                clickHandler(e){
                    console.log(1)
                    history.pushState({},'',this.to)
                    this.$router.data.current = this.to
                    e.preventDefault()
                }
            }
        })

        const _this = this
        Vue.component('router-view',{
            render(h){
                const component = _this.routeMap[_this.data.current]
                return h(component)
            }
        })
    }

    initEvent(){
        window.addEventListener('popstate',() => {
            this.data.current = window.location.pathname
        })
    }

}